1. Field of the Invention
The present invention generally relates to a disc cartridge of a generally rectangular flattened configuration for removably accommodating a disc-shaped optical or magnetooptical recording medium and, more particularly, to a tamper-proof lid structure for the disc cartridge for substantially semipermanently locking the lid to avoid an unauthorized removal or replacement of the disc-shaped recording medium.
2. Description of the Prior Art
The disc cartridge of the type referred to above is disclosed in, for example, the Japanese Laid-open Patent Publication No. 5-243626, published in 1994. According to this publication, the disc cartridge comprises a generally rectangular flattened casing having an access opening defined at a rear end thereof so as to extend over the entire width thereof. This known disc cartridge also includes a generally elongated lid for selectively opening and closing the access opening to allow the disc-shaped recording medium, for example, the optical disc, to be removed from and inserted into the interior of the casing, respectively. In this known disc cartridge, since the difference between the width of the disc casing and the outer diameter of the disc-shaped recording medium within the disc casing is very small, the access opening is defined at a rear end of the disc casing and, on the other hand, the lid has an engagement wall formed integrally therewith to a shape similar to the shape of the access opening so that when and so long as the access opening is closed by the lid the engagement wall can be received within the disc cartridge through the access opening. This lid is pivoted at one end to one corner region at the rear end of the casing so that it can be swung 180.degree. or more between opened and closed positions. The opposite end of the lid structure has an elastic lock pawl formed integrally therewith such that, when and so long as the lid is in the closed position, the elastic lock pawl can be engaged in an engagement hole defined in a side wall of the disc cartridge to lock the lid structure in a locked condition. To open the lid, a pin or the like must be inserted into the engagement hole to forcibly disengage the lock pawl from the engagement hole.
The capability of the lid being selectively opened and closed is necessitated to allow an "encased" optical disc, that is purchased, for example, in the form as accommodated within the disc casing, to be replaced with a different, "uncased" optical disc that is separately purchased without the disc casing. As is well known to those skilled in the art, certain optical disc recording and/or reproducing devices (players) require the use of a dedicated disc casing and, on the other hand, not only can optical discs for use therewith be available in the form as encased within such a dedicated disc casing, but they are also available in the form as uncased, that is, without the dedicated disc casing. If the "encased" optical disc has audio and/or video information such as, for example, music and/or computer application software, recorded thereon, the capability of the lid being selectively opened and closed in the dedicated disc casing makes it possible for the user to replace the encased optical disc with an "uncased" blank optical disc so that the user can record audio and/or video information on such blank optical disc on his or her own or at his or her will.
The capability of the lid being selectively opened and closed in the prior art disc cartridge often poses a problem. If the optical disc, regardless of whether it is an encased optical disc or whether it is an uncased optical disc, is improperly or disorderly handled or stored outside the disc casing, to such an extent as to have scratches and/or stubborn dirt on one or both surfaces thereof, such optical disc may be no longer useable for recording or reproducing audio and/or video information. Also, with the prior art disc cartridge, it may also happen that no one can discern at first sight if the disc cartridge he or she has happened to own is a quality product warranted by the manufacturer or if it contains an optical disc different from the original optical disc which ought to have been in it. Another possible problem with the prior art disc cartridge is that since the optical disc can easily be removed out of the disc casing, the optical disc is susceptible to tamper, i.e., information recorded on the optical disc may be forged or inadvertently or erroneously overwritten.